Sewing machines that rely on means other than an electric motor as a source of motive power for one or all of their functions generally fall into two categories, those that use a hydraulic drive and those that use air pressure. U.S. Pat. No. 4,690,081 discloses a sewing machine that has a separate hydraulic drive for each moving element and the courses of movement of the individual elements are synchronously controlled and adapted to each other by means of a hydraulic pulse generator control unit. Sewing machines of this type are extremely complex devices which require precise, split-second control of each element in conjunction with the others to ensure consistent and uniform sewing results and are primarily used in the garment industry. Other sewing machines, such as, for example, that shown in U.S. Pat. No. 3,353,511, use a pneumatic cylinder and piston to actuate only one element such as the presser foot or, for example, that shown in U.S. Pat. No. 3,913,508 wherein the pistons in pneumatic cylinders are used to drive only the needle bar.
Applicant is unaware of any sewing machine which utilizes separate pneumatically actuated pistons to both reciprocate the needle bar and rotate the bobbin mechanism, lift and lower the presser foot and tighten the thread to set the stitch after it has been formed and coordinate the operation thereof by means of a plurality of mechanically actuated pneumatic valves to achieve a smooth yet forceful stitching operation.
It is, therefore, the primary object of the present invention to provide a completely pneumatic sewing machine.
It is another object of the present invention to provide a sewing machine wherein the needle bar, bobbin mechanism, presser foot and stitch tightening mechanism are all controlled by pneumatically actuated pistons and associated mechanically actuated valves.
It is yet another object of the present invention to provide a pneumatically operated sewing machine which, due to its simple construction, is easy to maintain yet is highly reliable in its operation and relatively inexpensive to manufacture.
It is a still further object of the present invention to provide a pneumatically operated sewing machine that has relatively few moving parts and is devoid of complex gearing associated with electric motor driven sewing machines of the prior art normally associated with the leather fabrication industry.
These and other objects and purposes of this invention will be understood by those acquainted with the design and construction of sewing machines upon reading the following specification and the accompanying drawings.